1. Field of the Invention
The present invention relates to developing devices, image forming apparatuses, and image forming systems.
2. Description of the Related Art
(1) Image forming apparatuses such as laser beam printers are well known in the art. Such image forming apparatuses are provided with, for example, a photoconductor for bearing a latent image, and a developing device that is attachable to and detachable from the body of the image forming apparatus (or to/from a movable attach/detach section provided on the body of the image forming apparatus) and that is for developing the latent image borne on the photoconductor with a developer. When the image forming apparatus receives image signals etc. from an external device such as a host computer, it positions the developing device at a developing position which is in opposition to the photoconductor, develops the latent image borne on the photoconductor with the developer contained in the developing device to form a developer image, and transfers the developer image onto a medium to ultimately form an image on the medium.
In order to achieve, for example, the above-described function of developing the latent image borne on the photoconductor, the developing device of the above-described type is provided with a developer bearing roller for bearing the developer. The developing device develops the latent image borne on the photoconductor with the developer borne on the developer bearing roller.
The developing device is further provided with a first driving wheel that is provided on an end of the developer bearing roller for driving the roller, and a second driving wheel for transmitting a drive force to the first driving wheel. When the developing device is attached to the body of the image forming apparatus, the second driving wheel receives the drive force from the body of the image forming apparatus and transmits this drive force to the first driving wheel. The developer bearing roller is driven in this way. (See, for example, JP 2004-191524 A.)
It is, however, necessary for the first driving wheel and the second driving wheel to be positioned with high accuracy in order to appropriately drive the developer bearing roller. In developing devices in which the first driving wheel and the second driving wheel are not positioned with high accuracy, the developer bearing roller will not be driven appropriately, which may result in inappropriate developing operations.
(2) Another type of developing device is further provided with a positioning member for positioning the drive-system members such as the first driving wheel and the second driving wheel. This positioning member may be provided as two independent members (parts) in consideration of, for example, easy assembly of the developing device. The positioning member is provided with a positioning pin for positioning the developing device with respect to the body of the image forming apparatus when the developing device is attached thereto. (See, for example, JP 2004-191524 A.)
In order to let the developing device achieve appropriate developing operations, it is necessary to drive the developer bearing roller appropriately. On the other hand, in order to drive the developer bearing roller appropriately, it is necessary to design the developing device etc. so that the above-mentioned second driving wheel can appropriately receive the drive force from the body of the image forming apparatus.
In cases where the second driving wheel cannot appropriately receive the drive force from the body of the image forming apparatus, then it will become difficult for the second driving wheel to transmit a sufficient amount of drive force to the first driving wheel, which may cause inappropriate driving of the developer bearing roller and result in inappropriate developing operations.
(3) In order to achieve, for example, the above-described function of developing the latent image borne on the photoconductor, a developing device of another type has, in addition to the developer bearing roller for bearing the developer, a developer supplying roller for supplying the developer to the developer bearing roller. The developing device develops the latent image borne on the photoconductor with the developer supplied by the developer supplying roller and borne on the developer bearing roller.
The developer bearing roller and the developer supplying roller are mounted, respectively, on separate members, that is, an assembly member which is an example of a “first attachment member”, and a housing which is an example of a “second attachment member”. (See, for example, JP 2004-191524 A.)
In order to make the developer supplying roller appropriately achieve its function of supplying the developer to the developer bearing roller, it is necessary to position the developer supplying roller and the developer bearing roller with high accuracy. Further, it is preferable that this positioning is achieved with a simple structure.
(4) Furthermore, another type of developing device has a second gear wheel that meshes with a first gear wheel provided in the body of the image forming apparatus when the developing device, in a state attached to the attach/detach section, is moved up to a predetermined position along with the movement of the attach/detach section. The second gear wheel is supported by a second-gear-wheel shaft which, in turn, is supported on the body of the developing device by a supported section. (See, for example, JP 2001-228660 A.)
When the developing device is moved up to the above-mentioned predetermined position along with the movement of the attach/detach section, the first gear wheel and the second gear wheel come in to contact. At this time, the second-gear-wheel shaft may bend due to an external force applied through the second gear wheel.